Abstract
New research facilities like MEGa–Ray (Livermore) or ELI–NP (Bucharest) will provide within the next years (2013–2016) photon beams of unprecedented quality with respect to both photon intensity (total flux ~ 1013 γ/s) and spectral intensity (~ (104–106)/eVs), thus exceeding the performance of existing facilities by severalorders of magnitude. This tremendous progress will be enabled by Compton-backscattering of an intense laser off a high-quality electron beam, in conjunction with novel refractive bremsstrahlung beams focusing γ optics and efficient monochromatization techniques. We envisage to employ these γ beams for photofission studies on extremely deformed nuclear states of actinides, investigating their multiple–humped potential energy landscape in a highly selective way. Transmission resonances in the prompt fission cross section from the (superdeformed) second and (hyperdeformed) third potential minimum will be studied, where the fission decay channel can be expressed as a tunnelling process of these gateway states through the multiple–humped fission barrier.
Highlights
New research facilities like MEGa-Ray (Livermore) or Extreme Light Infrastructure’ (ELI)-NP (Bucharest) will provide within the years (2013-2016) photon beams of unprecedented quality with respect to both photon intensity
As outlined by [23], the broad structure of the isomeric shelf is predicted to be intrinsically composed of a multitude of individual sharp resonances, which so far could not be resolved. All these findings clearly indicate the presence of sharp fission resonances throughout the energy range around the fission barrier top down to the region of the isomeric shelf, calling for a consistent investigation over the full energy range with highest resolution
In order to prepare for photofission experiments at the nextgeneration γ-beam facilities like ELI-Nuclear Physics (ELI-NP), an exploratory experiment has been performed at the HIγS facility
Summary
MeGaRay (Livermore, [5]) or ELI-Nuclear Physics (Bucharest/Romania, [9]), novel perspectives open up for photonuclear science in general and photofission studies of the multiple-humped fission barrier landscape in particular. As outlined by [23], the broad structure of the isomeric shelf is predicted to be intrinsically composed of a multitude of individual sharp resonances, which so far could not be resolved All these findings clearly indicate the presence of sharp fission resonances throughout the energy range around the fission barrier top down to the region of the isomeric shelf, calling for a consistent investigation over the full energy range with highest resolution. Th not even the existence of a fission isomer in the second potential minimum could be directly observed, Zhang et al [22] concluded via level density arguments from their photofission data the ground-state excitation energy of the second potential minimum as 2.8 MeV. Fission resonances should appear in the prompt fission cross section at about 5.6 MeV, originating from the second potential minimum, while for lower excitation energies resonances from the third potential well are predicted to appear around 5.15 MeV and 4.5 MeV, respectively
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